1. Field of the Invention
The present invention relates to an apparatus and method for drying a substrate such as a semiconductor wafer, a glass substrate for a liquid crystal display panel, a mask substrate for a semiconductor producing device or the like, by removing liquid droplets on the substrate.
2. Description of the Background Art
One of the well known types of substrate drying apparatuses requires rotation of the substrate to remove wiping out droplets adhering to the surface of the substrate. Such an apparatus includes a chamber with an opening through which plural substrates enter and exit the chamber, a cover for closing the opening to prevent droplets of the substrates from being splashed out through the opening when substrates are subject to a drying operation by rotation, a filter provided on the cover for introducing ambient air inside the chamber, rotation means for holding the substrates in the chamber and for rotating the substrates, and an exhaust section for exhausting the ambient air sucked through the filter out of the chamber. In this rotation type substrate drying apparatus, the principal of drying the substrate lies in a use of centrifugal force generated by rotation means to blow away droplets in a radial direction of the substrate and a use of a flow of air sucked in through the filter by the rotation of the rotation means, i.e., the sucked in air flows over the surface of the substrate to enhance drying operation.
In another conventional type substrate drying apparatus (as described in Japanese Unexamined Patent Publication No 62-142328), it is proposed, for enhancement of the drying process, that ethanol be supplied over the surface of the substrate to replace the liquid droplets adhering over the substrate surface with supplied ethanol droplets and then the substrate is subject to drying by rotation of the substrate.
These conventional substrate drying apparatuses described in the above have one thing in common, that is, to intake the ambient air into the chamber the surface of the substrate being rotated in the chamber is exposed to oxygen contained in the sucked in ambient air. When the substrate being dried with exposure of oxygen an oxidation is subject to occur at the boundary between the substrate surface and the liquid droplets. The same kind of oxidation is subject to occur at the three dimensional structure of the device such as trenches. The oxidation if it occurs at the boundary, it will cause a problem in a film formation process in a later stage, resulting in poor production efficiency of the substrate manufacturing line comprising the above mentioned apparatus.